Neutral polymer bonding agents, their preparation methods, and their applications in solid propellants

Abstract

This invention relates to the field of solid propellant technology, specifically disclosing a neutral polymer bonding agent, its preparation method, and its application in solid propellants. The neutral polymer bonding agent is prepared by polymerization of poly(hydroxyalkyl polyacrylate) and cyanoacetic acid as raw materials. It can achieve controllable molecular weight and controllable proportion of functional groups in the polymer. Moreover, the active group -CN in the neutral polymer bonding agent has low steric hindrance and is more easily adsorbed on the surface of ammonium nitrate particles, thereby improving the bonding effect.

Description

Technical Field

[0001] This invention relates to the field of solid propellant technology, specifically to a neutral polymer bonding agent, its preparation method, and its application in solid propellants. Background Technology

[0002] Since Kim invented neutral polymer bonding agents (NPBA) in 1990, they have been widely used in nitrate ester plasticized polyether propellants, effectively improving the mechanical properties of these propellants. The molecular weight, hydroxyl content, and cyano content of NPBA determine its application performance. Traditional NPBA synthesis methods mainly use acrylonitrile, hydroxyethyl acrylate, etc., as raw materials, azobisisobutyronitrile (AIB) as an initiator, and a mercapto compound as a chain transfer agent, achieving the synthesis of the target polymer molecule through free radical polymerization. However, due to the different polymerization rates of acrylonitrile and hydroxyethyl acrylate, and the different conversion rates of the reactants, this method makes it difficult to simultaneously control the molecular weight and monomer ratio of NPBA, resulting in difficulty in obtaining NPBA with specific molecular weight and hydroxyl content, which adversely affects its application performance. The NPBA prepared by this method has a wide molecular weight distribution, which is not conducive to its bonding effect. Furthermore, the -CN group in the NPBA molecule prepared by this method that reacts with ammonium nitrate is in the secondary position, resulting in a large steric hindrance effect, further inhibiting its adsorption on the ammonium nitrate surface. Therefore, the NPBA with controllable molecular weight and functional group ratio developed in this invention has important application value. Summary of the Invention

[0003] This invention provides a neutral polymer bonding agent, its preparation method, and its application in solid propellants; it features controllable molecular weight and functional group ratio. Furthermore, its active -CN groups have low steric hindrance, making them more easily adsorbed onto the surface of ammonium nitrate solids, thus improving the bonding effect.

[0004] The technical solution of the present invention is to provide a neutral polymer bonding agent, the molecular structure of which is as follows:

[0005] ;

[0006] The R group is either methyl or hydrogen, and m and n represent the ratio of the two monomers, with m accounting for 70% to 95% and n accounting for 5% to 30%.

[0007] Optionally, the polymer molecular weight is 3000~50000.

[0008] This invention also relates to a method for preparing the aforementioned neutral polymer bonding agent, comprising the following steps:

[0009] S1. Dissolve polyalkyl acrylate in a solvent, add cyanoacetic acid, dehydrating agent and catalyst, and heat to carry out the reaction;

[0010] The materials obtained from S2 and S1 are washed with water and organic solvents respectively to remove byproducts. The resulting solid phase is dried to obtain the neutral polymer bonding agent.

[0011] Optionally, the polyhydroxyalkyl acrylate is polyhydroxyethyl methacrylate or polyhydroxyethyl acrylate, with a molecular weight of 2000~40000.

[0012] Optionally, the molar amount of cyanoacetic acid is 0.70 to 0.95 times the mass of poly(hydroxyethyl methacrylate) or poly(hydroxyethyl acrylate) divided by 116 or 130.

[0013] Optionally, the dehydrating agent is dicyclohexylcarbodiimide, diisopropylcarbodiimide, or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

[0014] Optionally, the catalyst is 4-N,N-dimethylpyridine, 4-pyrrolidinylpyridine, or 1-hydroxybenzotriazole.

[0015] Optionally, the heating temperature in S1 is 40~60℃; the reaction time is 4~10 hours.

[0016] Optionally, the organic solvent in S1 is dichloromethane; the organic solvent in S2 is one or more of methanol, ethanol, ethyl acetate or diethyl ether, including but not limited to.

[0017] This invention also relates to the application of the neutral polymer bonding agent in the preparation of composite solid propellants.

[0018] The present invention has the following beneficial effects:

[0019] This invention provides a neutral polymer bonding agent prepared by polymerization of poly(hydroxyalkyl acrylate) and cyanoacetic acid. It solves the problem of difficulty in simultaneously controlling molecular weight and monomer ratio caused by the different polymerization rates of the two monomers during the copolymerization of acrylonitrile and hydroxyethyl acrylate. It enables controllable molecular weight and controllable ratio of functional groups in the polymer. Furthermore, the -CN group in this neutral polymer bonding agent is a primary position with low steric hindrance, making it easier to adsorb onto the surface of ammonium nitrate particles, thereby improving the bonding effect.

[0020] The neutral polymer bonding agent of the present invention has the advantages of simple operation, mild reaction conditions, and simple post-processing. Detailed Implementation

[0021] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the raw materials, reagents, and other materials used in the following examples are commercially available products.

[0022] This invention provides a neutral polymer bonding agent, the molecular structure of which is as follows:

[0023] ;

[0024] The R group is either methyl or hydrogen, and m and n represent the ratio of the two monomers, with m accounting for 70% to 95% and n accounting for 5% to 30%; the molecular weight is 3000 to 50000.

[0025] The preparation of the above-mentioned neutral polymer bonding agent includes the following steps:

[0026] S1. Dissolve polyalkyl acrylate in a solvent, add cyanoacetic acid, dehydrating agent and catalyst, and heat to carry out the reaction;

[0027] The materials obtained from S2 and S1 are washed with water and organic solvents respectively to remove byproducts. The resulting solid phase is dried to obtain the neutral polymer bonding agent.

[0028] In some embodiments, the polyhydroxyalkyl acrylate is polyhydroxyethyl methacrylate or polyhydroxyethyl acrylate, with a molecular weight of 2000-40000.

[0029] In some embodiments, the molar amount of cyanoacetic acid is 0.70 to 0.95 times the mass of the raw polymer feed divided by 116 or 130.

[0030] In some embodiments, the dehydrating agent is one of dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide (DIC), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI), and its molar amount is 1.0 to 2.0 times that of the raw material cyanoacetic acid.

[0031] In some embodiments, the catalyst is one of 4-N,N-dimethylpyridine (DMAP), 4-pyrrolylpyridine (4-PPY), and 1-hydroxybenzotriazole (HOBt), and its molar amount is 0.02 to 0.15 times that of the raw material cyanoacetic acid.

[0032] In some embodiments, the organic solvent in S1 is dichloromethane; the organic solvent in S2 is one or more of methanol, ethanol, ethyl acetate or diethyl ether, including but not limited to.

[0033] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0034] Example 1

[0035] (1) Weigh 11.60 g of hydroxyethyl polyacrylate with a molecular weight of 2000 and add it to a three-necked reaction flask equipped with a stirrer, reflux condenser and thermometer. Add 300 mL of dichloromethane and turn on the stirrer until the polymer is completely dissolved.

[0036] (2) Add 7.65g of cyanoacetic acid, 20.39g of DCC and 1.10g of DMAP to the system in step one, heat the reaction system to 50℃ and reflux for 7h until the cyanoacetic acid is completely reacted.

[0037] (3) Add water to the system in step two and wash three times, then wash three times with ethanol to obtain wet product micelles. Dry the wet product in an oven at 90°C to obtain the product.

[0038] The obtained product was tested by GPC, and the molecular weight was 3000, with m accounting for 90% and n accounting for 10%.

[0039] Example 2

[0040] (1) Weigh 13.00 g of poly(hydroxyethyl methacrylate) with a molecular weight of 10,000 and add it to a three-necked reaction flask equipped with a stirrer, reflux condenser and thermometer. Add 400 mL of dichloromethane and turn on the stirrer until the polymer is completely dissolved.

[0041] (2) Add 6.88g of cyanoacetic acid, 15.12g of DIC and 1.20g of 4-PPY to the system in step one, heat the reaction system to 40℃ and reflux for 9h until the cyanoacetic acid reaction is complete.

[0042] (3) Add water to the system in step two and wash three times, then wash with methanol three times to obtain wet product micelles. Dry the wet product in an oven at 90°C to obtain the product.

[0043] The resulting product has a molecular weight of 14,000, with m accounting for 80% and n accounting for 20%.

[0044] Example 3

[0045] (1) Weigh 13.00 g of poly(hydroxyethyl methacrylate) with a molecular weight of 30,000 and add it to a three-necked reaction flask equipped with a stirrer, reflux condenser and thermometer. Add 400 mL of dichloromethane and turn on the stirrer until the polymer is completely dissolved.

[0046] (2) Add 5.95g of cyanoacetic acid, 24.10g of EDCI and 1.13g of HOBt to the system in step one, heat the reaction system to 60℃ and reflux for 8h until the cyanoacetic acid is completely reacted.

[0047] (3) Add water to the system in step two and wash three times. After washing three times with ethyl acetate, wet product micelles are obtained. Dry the wet product in an oven at 90°C to obtain the product.

[0048] The resulting product has a molecular weight of 41,000, with m accounting for 70% and n accounting for 30%.

[0049] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A neutral polymer bonding agent, characterized in that, The molecular structure of this neutral polymer bonding agent is as follows: ； Where R is a methyl group or hydrogen, m and n represent the number of repeating units of the two monomers, with m accounting for 70%~95% and n accounting for 5%~30%; The preparation method of this neutral polymer bonding agent includes the following steps: S1. Dissolve polyhydroxyalkyl acrylate in a solvent, add cyanoacetic acid, dehydrating agent and catalyst, and heat to react; the polyhydroxyalkyl acrylate is polyhydroxyethyl methacrylate or polyhydroxyethyl acrylate, with a molecular weight of 2000~40000. The materials obtained from S2 and S1 are washed with water and organic solvents respectively to remove byproducts. The resulting solid phase is dried to obtain the neutral polymer bonding agent.

2. The neutral polymer bonding agent according to claim 1, characterized in that: The neutral polymer bonding agent has a molecular weight of 3000~50000.

3. The neutral polymer bonding agent according to claim 1, characterized in that: The molar amount of cyanoacetic acid is 0.70 to 0.95 times the mass of poly(hydroxyethyl methacrylate) feed divided by 130; or 0.70 to 0.95 times the mass of poly(hydroxyethyl methacrylate) feed divided by 116.

4. The neutral polymer bonding agent according to claim 1, characterized in that: The dehydrating agent is dicyclohexylcarbodiimide, diisopropylcarbodiimide, or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

5. The neutral polymer bonding agent according to claim 1, characterized in that: The catalyst is 4-N,N-dimethylpyridine, 4-pyrrolidinylpyridine, or 1-hydroxybenzotriazole.

6. The neutral polymer bonding agent according to any one of claims 1 to 5, characterized in that: The heating temperature in S1 is 40~60℃; the reaction time is 4~10 hours.

7. The neutral polymer bonding agent according to any one of claims 1 to 5, characterized in that: The solvent in S1 is dichloromethane; the organic solvent in S2 is one or more of methanol, ethanol, ethyl acetate or diethyl ether.

8. The use of the neutral polymer bonding agent according to any one of claims 1 to 7 in the preparation of composite solid propellants.

Images